Avoid get same timestamps in log testcase

for arm64, userspace get time by vDSO, no syscall overhead.
multiple_test_2 sometimes get 2 same timestamps now, then testcase
fails.

Bug: b/135555666
Test: ./CtsLogdTestCases64 --gtest_filter=*multiple_test*
1 file changed
tree: 84a50bb9ba346b9de5c9599a3b3967b86e22eeda
  1. liblog/
  2. logcat/
  3. logd/
  4. logwrapper/